1. Field of the Invention
This invention relates to methods for producing self-locking fasteners and more particularly relates to improved methods for producing metallic self-locking fasteners having a metallic patch flame sprayed thereon.
2. Description of the Prior Art
Methods for producing threaded metallic self-locking fasteners having a metallic patch flame sprayed thereon are known in the prior art and may be seen be reference to allowed U.S. Ser. No. 121,664 filed Mar. 8, 1971, now U.S. Pat. No. 3,818,525 issued June 25, 1974 and allowed U.S. Ser. No. 287,206 filed Sept. 7, 1972, now U.S. Pat. No. 3,831,213 issued Aug. 27, 1974 both assigned to the assignee of this invention. In both of these applications, a threaded, metallic, reusable, self-locking, fastener is produced by spraying at least one molten metallic material over a selected portion of a threaded fastener to produce a metallic patch having a circumferential extension of less than 360.degree. and being thicker in the thread valleys than on the adjacent thread crests. Such patches have proven to be relatively porous and resilient and have provided self-locking fasteners having excellent locking and reusability characteristics. However, in some situations, the above mentioned methods have not been totally satisfactory as the bond between the patch and the threaded fastener was occasionally weaker than desired and also the porous outer surface of the patch occasionally caused a higher than desired frictional contact with mating threaded fasteners causing the initial installation torque required to threadably engage the self-locking fastener with a mating threaded fastener to be higher than desired and/or required. Also, if the patch were to be sprayed onto a previously heat treated threaded fastener additional preparatory steps such as grit blasting, dry air blasting, pre-heating and/or sizing might be required.